1. Field of the Invention
The present invention relates to semiconductor integrated circuit devices, and more particularly to silicon microwave monolithic integrated circuit devices and fabrication process.
2. Description of Related Art
The development of Silicon Microwave Monolithic Integrated Circuit (SiMMIC) devices has been limited due to an inability to integrate high Q inductors, transformers, and transmission lines with high frequency silicon bipolar junction transistors (BJTs). The fabrication of high frequency BJTs requires a silicon substrate or silicon epitaxial layer having a low resistivity, such as 1 to 10 ohm-cm. Unfortunately, when microstrip inductors, transformers, and transmission lines are incorporated with a low resistivity silicon substrate or silicon epitaxial layer, the resulting losses at high frequencies are unacceptable for the design of microwave transceivers. Thus, it has not been practical to integrate both high frequency BJTs and microstrip inductors, transformers and transmission lines in an SiMMIC device. Nevertheless, a low-loss SiMMIC device is highly desirable for UHF, L-Band, and S-Band transceivers because established large diameter silicon wafers and high yield batch processes offer the advantages of low cost and high reproducibility.